Substituted dithin tetroxide plant growth regulants

ABSTRACT

Regulation of the growth of plant life, including herbicidal, defoliant or desiccant effects, may be accomplished with certain 2,3-dihydro-1,4-dithin 1,1,4,4-tetroxides of the formula   WHEREIN THE R&#39;&#39;s have various values such as hydrogen, alkyl, etc. Certain of the compounds, such as 2,3-dihydro-5,6-dimethyl1,4-dithin 1,1,4,4-tetroxide, are new chemicals, and are useful as pre-and post-emergent herbicides, and in harvest aid procedures, such as defoliation/desiccation of various crops, including cotton and potatoes.

United States Patent [1 1 Brewer et a1.

[451 Nov. 18, 1975 1 SUBSTITUTED DITHIN TETROXIDE PLANT GROWTH REGULANTS [75] Inventors: Arthur D. Brewer, Guelph, Canada;-

Robert W. Neidermyer, Carmel, lnd.;.William S. Mclntire, Senatobia, Miss.

[731 Assignees: Uniroyal, Inc., New York, N.Y.;

Uniroyal Ltd., Quebec, Canada [22} Filed: May 7, 1973 21 Appl. Na; 357,757

[52] US. Cl. 71/73; 71/91; 260/327 P [51] Int. Cl. AOIN 9/12 [58] Fieldof Search 71/91, 73, 67; 260/327 P [56] References Cited UNITED STATES PATENTS 11/1962 Slezak et al 1. 71/91 l/l963 Strycker 260/327 P 3,082,214 3/1963 Bluestone 260/327 P 3,503,991 3/1970 Elsfeld et al 260/327 P 3,753,677 8/1973 Lamb et 211...; 71/67 3,755,362 8/1973 Asinger et al 260/327 P OTHER PUBLICATIONS Asinger et a1, 11, Zar Kenntis der Umsetzung von etc; (1971) Ann. Chem. 753 pp. 151-168 (1971).

Primary ExaminerGlennon l-l Hollrah Attorney, Agent, or Firm.lames J. Long [57 1 ABSTRACT Regulation of the growth of plant life, including herbicidal, defoliant or desiccant effects, may be accomplished with certain 2,3-dihydro-1,4-dithin l,1,4,4- 'tetroxides of the formula af S 1 19 Claims, No Drawings SUBSTITUTED DITHIN TETROXIDE PLANT GROWTH REGULANTS control of weeds is of great economic importance.

Weed competition inhibits the production of foilage, fruit or seed of agricultural crops. The presence of weeds may also reduce the quality of the harvested crop and reduce harvesting efficiency. Weed control is essential for maximum production of many agronomic and horticultural crops including com (Zea mays L.), rice (Oryza sativa L.) and soybeans (Glycine max (L.) Merr.). Weeds on non cropped areas may cause a fire hazard, undesirable drifting of sand or snow, irritation to persons with allergies and impaired beauty of the landscape. Aquatic weeds impede the flow of water and the progress of watercraft in canals and recreational waterways. algae'are unsightly and cause unpleasant odors in recreational watersas well as water reservoirs. Thus, suppression of undesirable weed and algae growth would have many advantages.

The invention, in one aspect, is based on the discovery that certain 2,3-dihydro-l,4-dithiin l,l,4,4-tetroxides are remarkably effective preemergence and postemergence herbicides, aquatic herbicides and algicides.

Another form of regulation of plant growth that is of great economic importance is represented by the use of harvest acid chemical compounds. Harvest aid includes such procedures as desiccation and defoliation of crop leaves, desiccation of vines, regrowth control of certain crops such as cotton, the forcing of maturity of certain crops and abscission of fruit.

It will be understood that many crops growing under optimum conditions do not mature uniformly or soon enough to facilitate mechanical harvesting. Crops such as cotton, potatoes and sunflowers frequently require either desiccation or defoliation of foliage before harvesting can be accomplished. By defoliating cotton, mechanical pickers can be utilized more efficiently because of three factors. One, the leaves do not interfere with the actual picking process; two, leaves do not cause excess trash accumulation or staining of fiber; and three, the top bolls mature, allowing a once through the field type of harvest. Cotton defoliation with organic chemicals is a common practice and is described in [1.8. Pat. Nos. 2,955,803, Goyette, Oct. 11, 1960; and 2,965,467, Markley, Dec. 20, 1960. In one important aspect, the invention provides chemical compounds which not only defoliate cotton leaves but also aid in stopping regrowth of leaves. Regrowth stains the fibers green, which reduces quality, and may require another defoliant application.

Potato vines need to be killed in order to facilitate mechanical digging. By desiccating the leaves and vines, the tuber skins mature and are less susceptible to scarring by the digger. Sunflower is mechanically harvested, but to obtain top yields, the stalk must be free of leaves. This defoliation also ripens the seed uniformly and conditions the head for easy. plucking. Many types of fruit such as citrus must be pre-condi- 2 tioned for abscission if mechanical harvesting is desired. Citrus is picked mechanically by shaking the tree. Without an abscission or loosening agent the fruit will not fall uniformly, requiring excessive, potentially damaging tree shaking. This invention provides certain new 2,3-dihydro-l ,4-dithiin l,l,4,4-tetroxides which are remarkably useful as harvesting aids in the foregoing respects, because of their ability to desiccate, defoliate, or cause abscission.

The chemical compounds useful in regulating growth of plant life in accordance with the invention are2,3- dihydro-l ,4-dithiin l,l,4,4-tetroxides of the formula Chemicals of the foregoing class include: 2,3-dihydro' 5,6-dimethyl-l,4-dithiin l,l,4,4-tetroxide; 2-ethyl-5,6- dihydro-3-methyl-l,4-dithiin l,l,4,4-tetroxide; 2,3- dihydro-2 ,5 ,6-trimethyll ,4-dithiin l 1 ,4,4,-tetroxide; 5 ,6,7 ,8-tetrahydro-2-methyl-1,4-benzodithian l, l ,4 ,4- tetroxide; 2,3,6,7-tetrahydro-2-methyl-5H-cyclopental ,4-dithiin l l ,4,4-tetroxide; 2-ethyl-2,3-dihydro-5 ,6- dimethyl-l,4-dithiin l,l,4,4-tetroxide; 2,3-dihydro- 2,3,5,6-tetramethyll ,4-dithiin 1,1 ,4 ,4-tetroxide; 2- ethyl-S,6-dihydro-5,6-dimethyll ,4-dithiin l l ,4,4-tetroxide; 5 ,6,7,8-tetrahydro-2,3-dimethyll ,4-benzodithian l l ,4,4-tetroxide; 2-ethyl-5 ,6-dihydro-3 ,5- dimethyl- 1,4-dithiin l l ,4,4-tetroxide; 2-ethyl-5 ,6- dihydro-3 ,6-dimethyl-l ,4-dithiin l ,l ,4 ,4-tetroxide', 2,3- dihydro-2 ,S-dimethyl-l ,4-dithiin l ,l ,4 ,4-tetroxide; 2,3- dihydro-2 ,6-dimethyl-l ,4-dithiin l l ,4,4-tetroxide; 2- ethyl-5,6-dihydro-S-methyll ,4-dithiin l ,l ,4,4-tetroxide; 2-ethyl-5 ,6-dihydro-6-methyll ,4-dithiin l l ,4,4-

3 tetroxide; 2-ethyl-2,3-dihydro-5-methyl-1 ,4-dithiin 1 ,1 ,4,4-tetroxide; 2-ethyl-2,3-dihydro-6-methyll ,4- dithiin 1,1,4,4-tetroxide; 2,5-diethyl- 2,3-dihydro-l,4- dithiin 1 ,1 ,4,4-tetroxide; 2,6-diethyl-2,3-dihydro- 1 ,4-

dithiin 1,1,4,4-tetroxide; 40,5,6,7,8,8a-hexahydro-2,3-

dimethyl-l ,4-benzodithiin 1,1,4,4-tetroxide; 2-ethyl- 4a,5,6,7,8,8a-hexahydro-1 ,4-benzodithiin 1,1 ,4,4-tetroxide; and 5,6,7 ,S-tetrahydro- 1 ,4-benzodithian 1,1,4,4-tetroxide.

From the standpoint of herbicidal action, the invention contemplates application of any of the foregoing compounds, in herbicidally effective amount, to a locus where herbicidal effects are desired.

Certain of the foregoing compounds are especially useful as harvesting aids where effects such as defoliation, desiccation, abscission, or prevention of regrowth are desired, namely: 2,3-dihydro-5,6-dimethyl-1,4- dithiin 1 ,1 ,4,4-tetroxide; 2-ethyl-5,6-dihydro-3-methyl- 1,4-dithiin 1,1 ,4,4-tetroxide; 2,3-dihydro-2,5,6- trimethyl-l ,4-dithiin l ,1 ,4,4-tetroxide; 5,6,7,8-tetrahydro-2-methy ll ,4-benzodithian l ,1 ,4,4-tetroxide; 2,3,6,7-tetrahydro-2-methyl-5l-l-cyclopenta-l ,4-dithiin l, 1 ,4,4-tetroxide; 2-ethyl-2,3-dihydro-5 ,6-dimethyl- 1,4-dithiin 1,1 ,4,4-tetroxide; 2,3-dihydro-2,3,5 ,6-tetramethyl-1,4-dithiin 1,1 ,4,4-tetroxide; 2-ethyl-5,6- dihydro-S ,6-dimethy1-1,4-dithiin 1 1 ,4,4-tetroxide; 5 ,6,7,8-tetrahydro-2,3-dimethyl-1,4-benzodithian 1 ,1 ,4,4-tetroxide; 2-ethyl-5 ,6-dihydro-3 ,S-dimethyl- 1,4-dithiin 1,l,4,4-tetroxide; and 2-ethyl-5,6-dihydro- 3,6-dimethyl- 1 ,4-dithiin 1, 1 ,4,4-tetroxide.

in one aspect, the invention is directed to new chemicals, useful in the regulation of plant growth, represented by the compounds having the structural formula stated above, wherein R, R R and R are as stated above, provided further that when two of the Rs are connected together, not more than one remaining R is hydrogen. The preferred new chemicals are those useful as harvest aids as described above.

US. Pat. No. 3,755,362 Asinger etal., Aug. 28, 1973 (equivalent to German Pat..No. 1,957,860, Deutsche Gold und Silber Scheidenstalt, May 27, 1971,) sets forth the structural formulas but does not disclose the present chemicals, nor is any plant growth regulating activity disclosed.

L. Levine, in a paper given at an American Chemical Society Meeting in San Francisco, 1968 (p. P024) disclosed the following but did not disclose any plant growth regulating activity for the chemicals. The chemical of last formula is used as a herbicide in this invention; the other formulas represent compounts which are not active plant growth regulants.

Related chemicals have been reported in such references as: Henry et a1. JACS 71, 2271 (1949); Parham et a1. JACS 75, 1647 (1953); Parham et a1. JACS 76, 1068 (1954); Parham et a1. JACS 77, 1169 1955); and Massingill et al. J. Org. Chem. 35, 823 (1970). None of 5 v the chemicals shown in those references has the surprising and unexpected utility found in the present chemicals.

The 2,3-dihydro-l,4-dithiin I,l,4,4-tetroxides with which the invention is concerned may bemade, for example, either by oxidation of the corresponding dithiin ple, by two broad methods.

i. Reaction of an alpha-halocarbonyl compound such as an alpha-haloketone (III), or of an alpha-halo-betaketoester (IV), with a 1,2-dithiol (V), either in a basic followed by an acid medium, or in an acid medium throughout.

R 511 R" s R RICOCHXRZ 3 2 R s11 R S R III - v HX s R SH 1 R COCHXCO Et I SH IV R V (i) NaOH (I) or by oxidative decarboxylation of dithiin carboxylic acids (II):

1 1 CO H ii. Reaction of a I,2-dithiol (III), with a ketone or aldehyde (VI) having an alpha-methylene group, or with where the Rs have the values set forth above.

Dithiins and dithiin acids may be prepared, for exama beta-ketoester (VII), followed by halogenation and ring expansion of the dithiolane (VIII) so produced.

R 'SH RICOCHZRZ 1, R S 2 R" S R CHZR gig X2 i (ii) Base 3 R1 R3 S R2 vIII R+ SH R COCH CO Et VII S s R cu co sc R R (1) x ---D R (11) Base R S CO Et R3 S (i) NaOl-l VIII (ii) HCl 3 R S COZH In certain cases the method of preparation employed may lead to a mixture of two different isomers of a particular chemical. Such an isomeric mixture may be used directly, if desired, for plant growth regulating purposes in accordance with the invention. Resolution of the mixture into products richer in one or the other of the isomers may be undertaken but is not necessary. Also, if desired, individual isomers may be prepared separately by a suitable synthetic method, and employed as plant growth regulants as described below.

To use the present chemicals as plant growth regulants, the chemical is applied to a locus where such control is to be effected (i.e., either to the plant life itself and/or to the soil in which the plant is growing or to be grown), in an amount effective to regulate the growth of the plant in the manner desired. The amount employed follows conventional practice for such uses as herbicidal use of plant harvesting aid use (e.g., desiccation, defoliation, abscission of fruit, forcing of maturity; also control of regrowth), and the chemical is suitably applied as a formulation in accordance with conventional agricultural chemical practice.

Thus, the chemical may be impregnated on finelydivided or granular inorganic or organic carriers such as attapulgite clay, sand, vermiculite, corn cobs, activated carbon or other granular carriers known to the art. The impregnated granules may then be spread on the soil. Furthermore, the chemical may be formulated, for example, as a wettable powder by grinding it into a fine powder and mixing it with an inactive powdered the chemical in a solvent such as benzene, toluene, or

other aliphatic or aromatic hydrocarbon to which a surface active dispersing agent has been added. The emulsifiable concentrate may then be dispersed in water and applied by spraying. The chemical may also be dissolved in water (for example, up to a concentration of 3000 ppm [parts per million] and mixed with a surface active agent before spraying. Water solubility may be increased using a cosolvent system involving acetone, dimethyl sulfoxide or other water miscible solvents. Suitable surface active agents are well known to those skilled in the art, and reference may be had to McCutcheons Detergents and Emulsifiers, 1970, Allured Publishing Corp., Ridgewood, New Jersey, or Hoffman et al. U.S. Pats. 2,614,916, cols. 2 to 4 and 2,547,724, cols. 3 and 4, for examples of appropriate surface active agents.

The concentration of active chemical in the formulation may vary widely, e.g., from 1 to 95%. The concentration of active chemical in dispersions applied to the soil or foliage is almost invariably from 0.002% to 75%. The chemical may also be dissolved in water at a concentration of, for example, 0.1 ppm to 2000 ppm for use as an algicide.

For use as a preemergence herbicide the chemical is frequently applied at rates of 0.05 to 25 pounds per acre to soil which contains weed and crop seed (either to the surface of the soil or incorporated into the upper one to three inches of soil). As a postemergence herbicide, the chemical is typically applied at rates of 0.05 to 40 pounds per acre to the foliage of weeds. The chemicals may be employed individually, or as a mixture of two or more chemicals.

For use as a harvesting aid, the chemical is typically employed at a concentration of from 0.005% to about 25% by weight, and applied at a rate usually equivalent to approximately 0.1 pound to pounds per acre. Or-

dinarily the chemical is applied to the plants at least two days before harvesting. The chemicals indicated previously are not only remarkable for their ability to desiccate and/or defoliate the plants, and to cause ab- .scission of fruit and to force maturity, but in addition make possible highly effective control of regrowth 1 (e.g., 95% control or more). The chemicals may be employed individually, or as mixtures of two or more of the chemicals.

The most suitable rate of application in any given case may depend on such factors as soil type, soil pH, soil organic matter content, the quantity and intensity of rainfall before and after treatment, the air and and soil temperature, light intensity and light duration per day. All of these factors can have an influence on the efficacy of the chemicals for a given plant growth control use.

The herbicidal use may include control of vegetation at industrial sites or selective weed control in crops such as corn, soybeans, carrots or rice.

Among the crops on which new chemicals of the invention are useful, particularly as harvesting aids, may be mentioned cotton (including the exceedingly difficult to defoliate California cotton), potatoes, sunflowencitrus, sugarbeets, sugarcane, peppers, milo, pineapple, tomatoes, grapes, and other crops such as are mentioned in U.S.- Pat. No. 3,689,246, Young, Sept. 5, 1972.

The results obtained in accordance with the invention are particularly surprising in view of the fact that the precursors of the described chemicals, that is, the corresponding unoxidized analoges themselves, are not active herebicides or harvest aid chemicals.

The following examples will serve to illustrate the practice of the invention in more detail.

EXAMPLE 1 a. 3-Chloro-2-butanone (106.5 g, 1 mole) was added over a period of 3 hours to a sitrred, externally cooled (0) solution of ethanedithiol (94 g, 1 mole) and p-toluenesulfonic acid (0.5 g). The mixture was stirred at 0 for about 6 hours then left overnight. Aqueous hydrochloric acid (17 mls) was separated. The mixture was dissolved in benzene (500 ml), and heated under reflux with water removal by means of a Dean-Stark trap; a further 2 ml water collected (total 19 ml, calc. 18 ml). The benzene was removed in vacuo to give a clear liquid which was distilled at reduced pressure to give 2,3 dihydro-5,6-dimethyl-1,4-dithiin as a colorless or slightly green liquid, bp 7274/0.7 mm (lit.) [.I. L. Massingill et al., J.A.C.S. 35, 823 (1970)] 1l2113/25 mm) yield 114 g. (78%). NMR (nuclear magnetic resonance) 1.86 6s), 3.12 (4s) CDCl IR (infra red), 2910 (shoulder); 1610, 1410 (sh); 1285 (sh); 1155 (sh); 1065, 865 (sh); 755 (sh).

b. 2,3-Dihydro-5,6-dimethyl-1,4-dithiin (146 g., 1 mole), dissolved in glacial acetic acid cc), was added dropwise to a refluxing solution of 35% hydrogen peroxide (250 cc) and glacial acetic acid (250 cc). There is an exothermic reaction. When addition was complete, the solution was refluxed a further five minutes. On cooling, long white needles appeared. These were collected and recrystallized from boiling water to give 2,3-dihydro-5,6-dimethyl-1,4-dithiin 1,1,4,4-tetroxide as long White needles, mp 166168, yield 166 g. (79%). NMR (CDCl 2.13 (6s), 3.93 (4s).

Anal. Calcd. for C T-1 0,5 C, 34.29; H, 4.86. Found: C, 34.25, 34.30; H, 4.81, 4.74. IR, 2980, 2940, 1550, 1400, 1300, 1180, 1100, 760.

EXAMPLE 2 a. The procedure of Example 1(a) is followed using 2-bromo-3-pentanone and ethanedithiol to give a 2- ethyl-5,6-dihydro-3-methyl-l,4-dithiin as a colorless oil, bp 8892/2.8 mm, yield 41%. NMR, 1.04-(3t), 1.88 (3s), 2.19 (2 1), 3.12 (4s). IR, 2920 (sh); 1600, 1410 (sh); 1285 (sh), 1155 (sh); 1065, 865 (sh); 755 (sh).

b. The procedure of Example 1(b) is followed to give 2-ethyl-5 ,6-dihydro-3-methyl-1,4-dithiin 1 ,1,4,4-tetroxide as white needles, mp l09-113, Yield 59%.

Anal. Calcd. for C H O S C, 37.50; H, 5.40. Found: C, 37.82, 38.17; H, 5.28, 5.44. NMR, 1.24 (3t), 2.16 (35), 2.55 (2q), 3.88 (4s) (CDCl IR, 2990, 2940, 1615, 1395, 1295,1175,1110, 765.

EXAMPLE 3 a. The procedure of Example 1(a) is repeated, using 1,2-propanedithiol and 3-chloro-2-butanone to give 2,3-dihydro-2,5,6-trimethyl-1,4-dithiin as a clear green liquid, bp 49.551/0.7 mm, yield 36.5%. NMR 1.36 (3d), 1.88 (6s), 2.4-3.6 (3m) (CDCl IR, 2905 (sh);

11 1825, 1410 (broad); 1250, 1155 (sh); 1065 (hr); 730, 7

b. The procedure of Example 1(b) is followed, giving 2,3-dihydro-2,5,6-trimethyl- 1 ,4-dithiin 1,1 ,4,4-tetroxide as white needles mp 1 l116, yield 49%.

Anal. Calcd. for C H, O.,S C, 37.50; H, 5.40. Found: C, 37.28, 37,78; H, 5.95, 5.29. IR, 2975, 1545, 1400, 1290, 1180, 1100, 755.

EXAMPLE 4 a. The procedure of Example 1(a) is followed using 2-chloro-cyclohexanone and 1,2-propanedithiol to give 5,6,7,8-tetrahydro-2-methyl-1,4-benzodithian as a greenish oil, bp 127-130/2.3 mm, Yield 66%. NMR, 1.36 (3d), 1.4-1.88 (4m), 1.88-23 (4m), 2.6-3.7 (3m). IR 2920, 1615, 1410, 1325, 1250, 1120, 855, 715.

b. The procedure of Example 1(b) is followed to give 5 ,6,7,8-tetrahydro-2-methyl-1,4-benzodithian 1 ,1 ,4,4- tetroxide as white needles, mp 158.5-159.5, Yield 61%.

Anal. Calcd. for C H O S C, 43.20; H, 560. Found: C, 43.26; H, 5.50. NMR, 1.57 (3d), 1.5-2.2 (4m), 2.3-3.0 (4m), 3.35-4.5 (3m), (CDCl IR, 2965, 2920, 1625, 1305, 1130, 880, 770, 695.

EXAMPLE 5 a. The procedure of Example 1(a) is followed using 2-bromocyclopentanone and 1,2-propanedithiol to give 2,3,6,7-tetrahydro-2-methyl-5H-cyclopenta-1,4- dithiin as a greenish oil, bp 92.593/1 mm, Yield 69%. NMR, 1.42 (3d), 1.6-2.2 (2m), 2.2-2.65 (4m), 2.5-3.7 (3m) (CDC1 IR 2920, 1605, 1420, 1310, 1260, 1125, 870, 720.

b. The procedure of Example 1(b) is followed to give 2,3,6,7-tetrahydro-2-methy1-5H-cyclopenta-1 ,4-dithiin 1,l,4,4-tetroxide as white crystals, mp 158-161, Yield 64%.

Anal. Calcd. for C H O S C, 40.68; H, 5.12. Found: C, 41.23, 40.65; H, 5.16. NMR, 1.45 (3d) 1.8-2.4 (2m), 2.92 (4t), 3.75-4.35 (3m) (DMSO). IR, 1610, 1310, 1240, 1190, 1130, 900, 780, 690.

EXAMPLE 6 a. The procedure of Example 1(a) is repeated, using 1,2-butanedithiol and 3-chloro-2-butanone to give 2- ethyl-2,3-dihydro-5,6-dimethyl-1,4-dithiin as a colorless oil, bp 68-8l/0.7, yield 35%, NMR 1.01 (3t), 1.4-2.9(2m), 1.87 (6s), 2.6-3.4 (3m). IR, 2910 (sh); 1610 (sh); 1410, 1220 (sh); 1155 (sh); 1070, 735, 700.

b. The procedure of Example 1(b) is repeated giving 2-ethyl-2,3-dihydro-5 ,6-dimethyl-1,4-dithiin 1 ,1 ,4,4- tetroxide as white needles, mp 103-105, yield 68%. NMR 1.16 (3t), 1.5-2.7 (2m), 1.65 (65), 3.4-4.0 (3m). IR, 2970, 2940, 1630, 1400, 1295, 1180, 1120, 750.

Anal. Calcd. for C H O S C, 40.34; H, 5.92. Found: C, 40.35, 40.05; H, 5.83, 5.71.

EXAMPLE 7 a. The procedure of Example 1(a) is followed using 2,3-butanedithiol and 3-chloro-2-butanone to give 2,3- dihydro-2,3,5,6-tetramethyl-1,4-dithiin, as a colorless liquid, b.p. 5860 /0.02 mm, yield 60%. NMR 1.34 (6d), 1.87 (6s), 2.7-3.2 (2m) (CDCl IR, 2950, 1600, 1435, 1365, 1150, 1060, 760, 680.

b. The procedure of Example 1(b) is followed to give 2,3-dihydro-2,3,5,6-tetramethyl-1,4-dithiin 1 ,1 ,4,4-tetroxide, as white crystals, m.p. 244246.5, yield 46%.

12 Anal. Calcd. for C H O S C, 40.34; H, 5.92. Found: C, 40.39; H, 6.15. NMR 1.54 (6d), 2.17 (65), 3.55-3.95 (2m) (CDCl IR 2940, 1630, 1445, 1300, 1180, 1115, 1065, 750.

EXAMPLE 8 a. The procedure of Example 1(a) is followed using 2,3-butanedithiol and l-chloro-2-butanone to give 2- ethyl-S,6-dihydro-5,6-dimethyl-1,4-dithiin as a colorless oil, b.p. 5558/0.030.05 mm, yield 53%. NMR 1.08 (3t), 1.36 (6d), 2.18 (2q), 2.7-3.1(2m), 5.78 (1s, broadened) (CDCl IR 3000 (shoulder), 2955, 1570, 1440, 1365, 1110, 825, 705.

b. The procedure of Example 1(b) is followed to give 2-ethyl-5 ,6-dihydro-5,6-dimethyl-1 ,4-dithiin 1 l ,4,4- tetroxide, as white crystals, m.p. 128-132. Yield 37%. NMR 1.23 (3t), 1.5 (6m), 2.66 (2, octet), 3.8 (2m), 6.51 (15, broadened). IR 3020, 2940, 1620, 1315, 1275, 1115, 955, 740.

EXAMPLE 9 a. The procedure of Example 1(a) is followed using 2,3-butanedithiol and 2-chlorocyclohexanone to give 5,6,7,8-tetrahydro-2,3-dimethyl-1,4-benzodithian as a greenish oil, b.p. 100/0.07 mm. Yield 49%. NMR 1.34 (6d), 1.45-2.25 (8m), 2.7-3.1 (2m). IR 2900, 1610, 1435, 1365, 1320, 1115, 795,690.

b. The procedure of Example 1(b) was followed to give 5,6,7,8-tetrahydro-2,3-dimethyl-1 ,4-benzodithian 1,1,4,4-tetroxide as white needles, mp. l92-195, yield 57%. NRM 1.54 (6d), 1.62.1 (4m), 2.4-2.8 (4m), 3.81 (2m), (CDC1 IR 2940, 1450, 1420, 1310, 1260, 1130, 965, 740.

EXAMPLE 10 a. The procedure of Example 1(a) was followed using 1,2-propanedithiol and 2-bromo-3-pentanone to give a mixture of 2-ethyl-5,6-dihydro-3,5-dimethyl-l ,4-dithiin and 2-ethyl-5,6-dihydro-3,6-dimethyl-1,4-dithiin as a greenish oil, b.p. 8590/3 mm, yield 29%. IR 2905, 1615, 1410,1215, 1155,1060, 735, 705.

b. The procedure of Example 1(b) was followed to give a mixture of 2-ethyl-5,6-dihydro-3,5-dimethyl-l ,4- dithiin 1,1,4,4-tetroxide and 2-ethyl-5,6-dihydro-3,6- dimethyl-l,4-dithiin 1,1,4,4-tetroxide as a clear, colorless, very viscous oil, yield 55%. NMR 1.01-1.38 (3t), 1.47-1.61 (3d), 2.16 (35), 2.38-2.75 (2q), 3.3-4.05 (3m). (CDCl IR 2970, 2930, 1620, 1310, 1170, 1110, 730, 690.

EXAMPLE 1 1 a. The procedure of Example 1(a) is followed, using chloroacetone and 1,2-propanedithiol to give a mixture of 2,3-dihydro-2,5-dimethyl-1,4-dithiin and 2,3-dihydro-2,6-dimethyl-1,4-dithiin as a colorless oil, bp 68-77/6 mm. NMR 1.39 (3d), 1.90 (3s), 2.5-3.65 (3m), 5.78 (1 quin). IR 3000, 2910,1585,1400,1350, 1090, 810, 760.

b. The procedure of Example 1(b) is followed to give a mixture of 2,3-dihydro-2,5-dimethyl-1,4-dithiin 1 1 ,4,4-tetroxide and 2,3-dihydro-2,6-dimethyl-1 ,4- dithiin l,l,4,4-tetroxide as long white needles, mp -205,

Anal. Calcd. for C H O S C. 34.29; H, 4.86. Found: C, 34.85; H, 4.81. NMR 1.51 (3d), 2.16-2.19 (3d), 3.6-4.2 (3m), 6.98 (1m) (CDCl -DMSO). IR 3010, 2970, 2920, 1620, 1400, 1300, 1120, 705.

EXAMPLE 12 I a. The procedure of Example 1(a) is followed using l-chloro-2-butanone and 1,2-propanedithiol to give a mixture of 2-ethyl-5,6-dihydro-5-methyl-1,4-dithiin 5 and 2-ethy1-5,6-dihydro-6-methyl 1,4-dithiin as an oil, bp 79-83/I.3 mm, yield 30%. NMR 1.08 (3t), 1.40 (3d), 2.18 (2q), 2.5-3.6 (3m), 5.83 (lq) (CDCl b. The procedure of Example l(b) is followed to give a mixture of 2-ethyl-5,6-dihydro-5-methyl-1,4-dithiin l,l,4,4-tetroxide and 2-ethyl-5,6-dihydro-6-methyl- 1,4-dithiin 1,1,4,4 -tetroxide as long white needles, mp 14l-153. Yield'55%.

' Anal. Calcd. for C H O S C, 37.50; H, 5.40. Found: C, 37.79, 37.59; H, 5.29, 5.23. NMR 1.18 (3t), 1.45 (3d), 2.52 (2q), 3.8-4.3 (3m), 7.28 (1) (DMSO). IR 3010, 2980, 2920, 1630, 1400, 1295, 1120, 705.

EXAMPLE 13 EXAMPLE 14 a. The procedure of Example 1(a) is repeated, using 1,2-butanedithiol and l-chloro-2-butanone to give a mixture of 2,5-diethyl-2,3-dihydro-1,4-dithiin and 2,6- diethyl-2,3-dihydro- 1 ,4-dithiin as a slightly greenish oil, bp 77-78/0.6; NMR 1.01 (3t), l.42.6 (2m), 1.32 (3t), 1.44 (2q), 2.6-3.4 (3m), 5.78 (1m), yield 69%. IR 3000, 2910, 1585, 1410, 1220, 1095, 810, 755.

b. The procedure of Example l(b) is repeated, giving a mixture of 2,5-diethyl-2,3-dihydro-1,4-dithiin 1 ,1 ,4,4-tetroxide and .2,6-diethyl-2,3-dihydro-1 ,4-dithiin l,l,4,4-tetroxide as white needles, mp 99-136, yield 65%.

Anal. Calcd. for C H O S C, 40.34; H 5.92. Found: C, 39.90, 40.31; H, 5.84, 5.90. NMR 1.17 (3t), 1.22 (3t), l.42.6 (2m), 2.63 (2q), 3.4-4.1 (3m), 6.47 (1m), (CDCl IR 3010, 2970, 1620, 1395, 1300, 1120, 760, 680.

EXAMPLE 15 a. The procedure of Example 1(a) was followed using 1,2-cyclohexanedithiol and 3-chloro-2-butanone to give 4a5 ,6,7,8,8a-hexahydro-2,3-dimethyl-1,4-benzodithiin as a colorless oil, bp l00102/0.2 mm. Yield 78%. NMR 1.07-2.2(8m), 1.85 (65), 2.9-3.2 (2m). IR 2924, 2850, 1615, 1440, 1335, 1275, 1180, 985.

b. The procedure of Example l(b) was followed to.

give 4a,5 ,6,7,8,8a-hexahydro-2,3-dimethyl-1,4-benzodithiin 1,1 ,4,4-tetroxide as white needles.

. 5 ,6,7 ,S-tetrahydro- 1 ,4-benzodithian y 14 Anal. Calcd. fOr C10H1504Sgi C, H, :Found: C, 45.65; H, 6.29.

EXAMPLE 16 a. To a boiling solution of 1,2-cyclohexanedithiol (44.4 g.) in benzene (250 ml) with a trace of p-toluenesulfonic acid was added l-chloro-2-butanone (31.8 g.) in benzene over 2 hrs. The solution was heated under reflux for 35 hours with water removal by means of a DeanStark trap. The reaction mixture was washed with cold aqueous sodium hydroxide and water, dried and reduced to an oil under vacuum. The crude 2-ethyl- 4a,5 ,6,7,8 ,8a-hexahydro- 1 ,4-benzodithiin was distilled at high vacuum to give a colorless oil mainly boiling at 100/0.1 mm. Yield 63%. NMR 1.09 (3t), 0.9-2.4 (8m), 2.19 (2q), 2.8-3.15 (2m), 5.80 (It) CDCl IR 3000, 2930, 1585, 1335, 1275, 1125, 875, 840.

b. The procedure of Example l(b) is followed to give 2-ethyl-4a,5 ,6,7 ,8 ,8a-he xahydro- 1 ,4-benzodithiin l,l,4,4-tetroxide as white needles, mp 140-142.

Anal. Calcd. for C H O S C, 45.45; H 6.10. Found: C, 45.82; H, 6.13. NMR 1.22 (3t), 1-2.6 (8m), 2.67 (2q), 3.6-3.9 (4d), 6.52 (It) CDCI Yield 64%. IR 3020, 2940, 1630', 1300, 1260, 1120, 760, 680.

EXAMPLE 17 a. The procedure of Example 1(a) is followed using 2-chlorocyclohexanone and ethanedithiol to give 5,6,7,8-tetrahydro-1,4-benzodithian as a greenish oil, bp /0.5 mm, yield 45%, NMR 3.18 (4s), ring protons. IR 2920, 1610, 1410, 1325, 1280, 1125, 1025, 785.

b. The procedure of Example l(b) is followed to give 1 1 ,4,4-tetroxide as large translucent crystals, mp 172-175, yield 41%.

Anal. Calcd. for C H O S C, 40.68; H, 5.12. Found: C, 40.77; H, 5.05. IR, 2990, 2935, 1630, 1400, 1300, 1125, 880, 750.

EXAMPLE 18 To illustrate effectiveness of the described dithiin tetroxides as preemergence herbidides, 600 mg chemical is dissolved in 10 ml organic solvent (e.g., acetone) to which 30 mg conventional emulsifying agent (e.g. isooctylpolyethoxyethanol Triton X [trademark]) is added. The solution is diluted to 100 ml with distilled water. Twenty milliliters of this 6000 ppm solution is diluted to 500 ppm with distilled water. The chemical is applied at the rate of 10 lb./A (pounds per acre) by drenching 23 ml of the 500 ppm solution on the surface of soil in 4 1/2-inch plastic pots which had been planted with the following weeds: rough pigweed (Amaranthus retroflexus L.), purslane (Portulaca oleracea L.), tall momingglory (Ipomea purpurea L. Roth), crabgrass (Digitaria ischaemum (Schreb.) Muhl.), Barnyardgrass (Echinochloa crusgalli (L) Beaur.), giant foxtail (Setaria faberi Herrm.) and southern nutsedge (Cyperus rotundus L.). The percent control of the weeds compared to untreated checks is determined two weeks after treatment. TABLE I shows the results with the preemergence herbicides of the invention prepared in accordance with the above examples.

TABLE I Dithiin Tetroxide Preemergence Herbicides Percent Control of Weeds at Rate of Lb/A Chem. Pig- Purs- Tall M. B-yard Crab- Fox- Nutof Ex. weed lane glory grass grass tail sedge l 100 100 I00 I00 I00 I00 50 2 100 100 0 60 I00 100 O V 3 I00 I00 50 I00 100 100 0 6 100 100 90 I00 100 100 0 I7 100 I00 95 98 100 I00 0 4 100 100 0 8O 50 90 0 I5 100 I00 95 65 100 100 0 I6 I00 I00 0 35 30 0 0 I3 I00 I00 60 0 0 l4 0 100 0 0 50 50 0 5 0 O 75 85 75 0 l l 100 I00 0 25 50 0 12 100 I00 0 85 100 I00 0 7 100 I00 73 90 95 95 0 8 I00 I00 25 90 95 100 0 9 9O 90 0 0 90 50 0 I0 I00 I00 82 98 I00 100 0 EXAMPLE l9 EXAMPLE 21 To illustrate effectiveness of the described dithiin tetroxides as postemergence herbicides, the 6000 ppm so- Selectivity of a herbicide is desirable since it allows control of weeds growing among desirable crop plants.

Iution described under Example 18 is atomized with a 25 To illustrate the usefulness of the dithiin tetroxides of conventional DeVilbiss sprayer, wetting the foliage to the drip point. The weeds, which are the same species as described under Example 18, are treated 6 days after emergence. The percent control is evaluated 2 weeks the invention as selective preemergence herbicides, 15 mg chemical dissolved in 5 ml organic solvent containing 25 mg conventional emulsifying agent and this solution diluted to 300 ml with distilled water. The chemiafter treatment. TABLE II shows the results with the 30 cal is applied at the rate of 2 lbs/A by drenching the postemergence herbicides of the invention.

TABLE II surface of soil containing weed and crop seeds in 6-inch Dithiin Tetroxide Postemcrgence Herbicides Percent Control of Weeds With 6000 PPM Solution Barn- Giant Chem. Pig- Purs- Tall M. yard Crab- Fox- Nutof Ex. weed lane glory grass grass tail sedge I 90 90 9O 90 90 90 25 2 100 8O 80 I00 0 3 100 100 100 I00 90 I00 0 6 98 100 I00 98 95 I0 7 I00 I00 I I0 75 25 l5 0 8 I00 0 90 I 5 IO 0 9 100 100 0 35 30 l5 0 I0 90 90 90 90 8O 80 0 lastic ots with 80 ml of the 50 m solution. The er- EXAMPLE 20 p p pp p To illustrate activity as an algicide and on aquatic herbicide, 5L of a 1000 ppm solution of the chemical of cent weed control and crop injury are evaluated two weeks after emergence of the crops. TABLE III illustrates the usefulness of these chemicals as selective pre- Example 1, namely, 2,3-dihydr0-5,6-dimethyl-l,4-dith- 50 emergence herbicides.

TABLE III Dithiin Tetroxide Selective Preemergence Herbicides Percent Weed Control and Crop Injury at Rate of ZLb/A Tall Barn- Giant Chem. Pig- Purs- Morn. yard Crab- Foxof Ex. weed lane Glory grass grass Tail Corn Rice I 100 100 100 I00 I00 100 40 60 I7 I00 I00 60 50 6O 0 0 3 I00 I00 100 I0 30 6 I00 100 90 90 I00 0 o iin l,l,4,4-tetroxide was poured into a plastic pot con- EXAMPLE taining green algae (Spirogyra) filaments and waterhyacinth (Eichornia crassipes (Mart) Solms) plants.

To illustrate the effectiveness of dithiin tetroxides of After ten days, containers of untreated water supported 65 the invention as harvest aid chemicals, specifically as an algae growth and live water hyacinth plants. However, the plants growing in the 1000 ppm solution died within 10 days.

desiccants or defoliants for cotton, 600 mg chemical is dissolved in either distilled water or 5 ml organic solvent (e. g., acetone) to which 30 mg conventional emulisoctyl polyethoxyethanol, Triton tional Devilbiss sprayer, wetting-the plant to the dripoff on 20 feet of Green Mountain White potato vines.-

" The vines were actively growing'at application time. Ten days after theapplications of spray solutions, the

point. Two weeks after the spraying, the plants are examined and an estimate of the percentage area of leaf tissue killed is made (the result is reported as percent desiccation, which is a manifestation of phytotoxicity, in TABLE IV) or the percentage of leaves which have dropped is estimated (the result is reported as percent .defoliation in TABLE IV). The chemicals shown to produce desiccation in TABLE IV will, at lower rates,

produce defoliation, which in many cases is more desirable.

TABLEIV Dithiin Tetroxide Cotton Desiccants/Defoliants Percent Desiccation/ Defoliation at 6000 PPM Chem. of Ex.

lOO Desiccation 85 Desiccation I Desiccation 100 Desiccation 100 Desiccation vI00 Defoliation I00 Desiccation 100 Desiccation 50 Desiccation 85 .Desiccation EXAMPLE 23 Defoliation response on cotton is further demonstrated in this example, together with the important property of regrowth inhibition. Four hundred and eighty mgs chemical is dissolved in either water or ml toluene, mixed homogeneously, and this solution diluted to 120 ml with water. Mature cotton plants with 4 to 5 well developed bolls are sprayed to the drip point with the desired chemical. Ten days after application of the chemical the percent defoliation is estimated and 30 days after application the plants are inspected for regrowth, with the results shown in-TABLE V, wherein the percent regrowth control is estimated by comparison with an untreated check plant.

TABLE V Mature Cotton Defoliant and Regrowth Test with Dithiin Tetroxides This example illustrates the effectiveness of 2,3-dihydro-5,6-dimethyl-l ,4-dithiin l,l,4,4-tetroxide as a harvest aid chemical on potatoes. Four g. this chemical was dissolved in 1000 ml water (50C) to give a 4000 ppm solution, and one-half percent of a surfactant (e.g., condensation product of trimethylnonanol with 6 to l3 moles of ethylene oxide, Adjuvan T [trademark] was added. A diluted 1000 ppm solution was also prepared. The solutions were sprayed to the point of run leaf defoliation, as well as vine kill, were 100%, with both solutions.

EXAMPLE 25 This example illustrates citrus abscission. The following materials were mixed to make. a dry powder:

Mgs

2,3-Dihydro5 ,-dimethyll ,4- dithiin l.l,4.4-tetroxide 200 Surfactants: Alkaryl polyether alcohol (Triton Xl20 ltrademarkl) 4 Sodium N-methyl-N-palmitoyl laurate v (lgepon TN-74 [trademarkh 4 Polymerized sodium salts of alkyl naphthalene sulfonic acid (Daxad-l l" [trademark] 8 Powders: Kaolin clay (Dixie Clay" [trademark]) 56 Silica ("Hi Sil 233" [trademark]) I28 The foregoing was suspended in 1000 ml water. This is equivalent to 200 ppm active chemical. Dosages of I00, 50 and 25 ppm were made from the 200 ppm stock solution. A single citrus (orange) branch with 30 fruits was marked and sprayed to runoff with each dilution. Seven days later degree of abscission was measured by recording the average number of pull pounds required to remove fruit from the branch. The data in TABLE VI illustrate the chemical abscission properties, expressed as the average pull from 10 fruit.

TABLE VI Abscission of Citrus with 2,3-Dihydro- 5,6-dimethyll ,4-dithiin l ,1 ,4,4-tetroxide 1. A method of aiding in the harvesting of the products of desirable plants comprising applying to the locus thereof, an effective amount of a 2,3-dihydro-l ,4- dithiin l,l,4,4-tetroxide of the formula wherein R R R and R are selected from the group consisting of hydrogen and lower alkyl having one to two carbon atoms, not more than two of the Rs being hydrogen, or an adjacent pair of Rs are connected together in the form of a chain of three to four methylene groups.

2. A method as in claim 1, wherein the Rs have sets of values as follows:

3. A method as in claim 1 in which the locus to which the chemical of the said formula is applied is a crop to be prepared for harvest, the chemical being applied in amount effective to prepare the crop for harvest, and the chemical being selected from the group consisting of: 2,3-dihydro-5,6-dimethyll ,4-dithiin l ,1 ,4,4-tetroxide; 2-ethyl-5,6-dihydro-3-methyl-l,4-dithiin l,l,4,4- tetroxide; 2,3-dihydro-2,5 ,6-trimethyll ,4-dithiin l ,1 ,4,4-tetroxide; 5,6,7 ,8-tetrahydro-2-methyl-l ,4-

benzodithian l,l,4,4-tetroxide; 2,3,6,7-tetrahydro-2- 20 aid effect is defoliation and/or desiccation with inhibition of regrowth.

6. A method as in claim 5 in which the said chemical is 2,3-dihydro-5 ,6-dimethyll ,4-dithiin l ,1 ,4,4-tetroxide.

7. A method as in claim 4 in which the said crop to which the chemical is applied is potatoes and the harvest aid effect is defoliation and/or desiccation.

8. A method as in claim 4 in which the said chemical is 2,3 -dihydro-5 ,6-dimethyll ,4-dithiin l ,1 ,4,4-tetroxide.

9. A method as in claim 4 in which the said chemical is 2-ethyl-5,6-dihydro-3-methyl-1,4-dithiin l,l,4,4-tetroxide.

10. A method as in claim 4 in which the said chemical is 2,3-dihydro-2,5,6-trimethyl-1,4-dithiin 1,1 ,4,4-tetroxide.

1 1. A method as in claim 4 in which the said chemical is 5 ,6,7 ,S-tetrahy dro-Z-methyl- 1 ,4-benzodithian 1 l ,4,4-tetroxide.

12. A method as in claim 4 in which the said chemical is 2,3,6,7-tetrahydro-2-methyl-5l-l-cyclopental ,4-dithiin l,l,4,4-tetroxide.

13. A method as in claim 4 in which the said chemical is 2-ethyl-2,3-dihydro-5 ,6-dimethyl-l ,4-dithiin 1 ,1,4,4- tetroxide.

14. A method as in claim 4 in which the said chemical is 2,3-dihydro-2,3,5,6-tetramethyl-1 ,4-dithiin l ,l ,4,4- tetroxide.

15. A method as in claim 4 in which the said chemical is 2-ethyl-5,6-dihydro-5,6-dimethyl-l,4-dithiin l,l,4,4- tetroxide.

16. A method as in claim 4 in which the said chemical is 5 ,6,7 ,8-tetrahydro-2,3-dimethyl-l ,4-benzodithian 1,1 ,4,4-tetroxide.

17. A method as in claim 4 in which the said chemical is 2-ethyl-5,6-dihydro-3 ,S-dimethyl-l ,4-dithiin l ,1 ,4,4- tetroxide.

18. A method as in claim 4 in which the said chemical is 2-ethyl-5,6-dihydro-3 ,6-dimethyl-l ,4-dithiin 1 ,l ,4,4- tetroxide.

19. A method of producing abscission of oranges comprising applying to an orange tree a composition comprising 2,3-dihydro-5 ,6-dimethyll ,4-dithiin l,1,4,4-tetroxide, in amount effective to produce abscission of the oranges, in admixture with a surface active agent, whereby harvesting of the oranges is aided. 

1. A METHOD OF AIDING THE HARVESTING OF THE PRODUCTS OF DESIRABLE PLANTS COMPRISING APPLYING TO THE LOCUS THEREOF, AN EFFECTIVE AMOUNT OF A 2,3-DIHYDRO-1,4-DITHIIN 1,1,4,4-TETROXIDE OF THE FORMULA
 2. A method as in claim 1, wherein the R''s have sets of values as follows:
 3. A method as in claim 1 in which the locus to which the chemical of the said formula is applied is a crop to be prepared for harvest, the chemical being applied in amount effective to prepare the crop for harvest, and the chemical being selected from the group consisting of: 2,3-dihydro-5,6-dimethyl-1,4-dithiin 1,1,4,4-tetroxide; 2-ethyl-5,6-dihydro-3-methyl-1,4-dithiin 1,1,4,4-tetroxide; 2,3-dihydro-2,5,6-trimethyl-1,4-dithiin 1,1,4,4-tetroxide; 5,6,7,8-tetrahydro-2-methyl-1,4-benzodithian 1,1,4,4-tetroxide; 2,3,6,7-tetrahydro-2-methyl-5H-cyclopenta-1,4-dithiin 1,1,4,4-tetroxide; 2-ethyl-2,3-dihydro-5, 6-dimethyl-1,4-dithiin 1,1,4,4-tetroxide; 2,3-dihydro-2,3,5,6-tetramethyl-1,4-dithiin 1,1,4,4-tetroxide; 2-ethyl-5,6-dihydro-5, 6-dimethyl-1,4-dithiin 1,1,4,4-tetroxide; 5,6,7,8-tetrahydro-2,3-dimethyl-1,4-benzodithian 1,1,4,4-tetroxide; 2-ethyl-5,6-dihydro-3,5-dimethyl-1,4-dithiin 1,1,4,4-tetroxide; and 2-ethyl-5,6-dihydro-3,6-dimethyl-1,4-dithiin 1,1,4,4-tetroxide.
 4. A method as in claim 3 in which the said chemical is applied in admixture with a surface active agent.
 5. A method as in claim 4 in which the said crop to which the chemical is applied is cotton and the harvest aid effect is defoliation and/or desiccation with inhibition of regrowth.
 6. A method as in claim 5 in which the said chemical is 2,3-dihydro-5,6-dimethyl-1,4-dithiin 1,1,4,4-tetroxide.
 7. A method as in claim 4 in which the said crop to which the chemical is applied is potatoes and the harvest aid effect is defoliation and/or desiccation.
 8. A method as in claim 4 in which the said chemical is 2,3-dihydro-5,6-dimethyl-1,4-dithiin 1,1,4,4-tetroxide.
 9. A method as in claim 4 in which the said chemical is 2-ethyl-5,6-dihydro-3-methyl-1,4-dithiin 1,1,4,4-tetroxide.
 10. A method as in claim 4 in which the said chemical is 2,3-dihydro-2,5,6-trimethyl-1,4-dithiin 1,1,4,4-tetroxide.
 11. A method as in claim 4 in which the said chemical is 5,6,7, 8-tetrahydro-2-methyl-1,4-benzodithian 1,1,4,4-tetroxide.
 12. A method as in claim 4 in which the said chemical is 2,3,6, 7-tetrahydro-2-methyl-5H-cyclopenta-1,4-dithiin 1,1,4,4-tetroxide.
 13. A method as in claim 4 in which the said chemical is 2-ethyl-2,3-dihydro-5,6-dimethyl-1,4-dithiin 1,1,4,4-tetroxide.
 14. A method as in claim 4 in which the said chemical is 2,3-dihydro-2,3,5,6-tetramethyl-1,4-dithiin 1,1,4,4-tetroxide.
 15. A method as in claim 4 in which the said chemical is 2-ethyl-5,6-dihydro-5,6-dimethyl-1,4-dithiin 1,1,4,4-tetroxide.
 16. A method as in claim 4 in which the said chemical is 5,6,7, 8-tetrahydro-2,3-dimethyl-1,4-benzodithian 1,1,4,4-tetroxide.
 17. A method as in claim 4 in which the said chemical is 2-ethyl-5,6-dihydro-3,5-dimethyl-1,4-dithiin 1,1,4,4-tetroxide.
 18. A method as in claim 4 in which the said chemical is 2-ethyl-5,6-dihydro-3,6-dimethyl-1,4-dithiin 1,1,4,4-tetroxide.
 19. A method of producing abscission of oranges comprising applying to an orange tree a composition comprising 2,3-dihydro-5,6-dimethyl-1,4-dithiin 1,1,4,4-tetroxide, in amount effective to produce abscission of the oranges, in admixture with a surface active agent, whereby harvesting of the oranges is aided. 